Hand-held power drills are widely used tools. When using such a drill, the operator is normally required to apply a substantial manual forward force to advance the drill bit into the work piece. This obviously requires effort from the operator and uses energy that could be utilized in other ways. Further, after a substantial amount of this type of drilling, the operator can become fatigued and subject to slow down and/or injury.
Of particular significance, it has been found that often drilling must take place where there is a restricted space in front of the hole to be drilled. The operator must hold the drill from the side. This makes it difficult for the operator to apply the necessary forward force on the drill bit. It is also difficult to keep the drill bit aligned at right angles to the work piece surface. Further, especially when large size drills are required it is difficult to hold up the weight of the drill from the side.
It is also often desirable for the operator to be able to control the rate of advancement of the drill bit into the work piece.
There have been various attempts to meet these needs, but they have all been lacking in various ways.
For example, U.S. Pat. No. 3,060,769 uses a complicated spring-loaded guide for advancing the drill bit. The spring is tensioned and it then applies an advancing force on the drill. This is not very satisfactory. The advancing force that the spring is capable of applying is rather limited. However, as stronger springs are used, the weight of the device undesirably increases. Further the force of each spring is a generally fixed value which cannot be varied during operation. This device also does not readily allow one to operate in tight spots.
Another attempt is disclosed in U.S. Pat. No. 3,089,357 that uses a guiding and advancing system that is very hard to attach to the drill and very difficult to use.